Methicillin-resistant Staphylococcus aureus and Vancomycin Prescribing in the Emergency Department: A Single-center Study Assessing Antibiotic Prescribing.

Abstract

Objectives: Given the support for methicillin-resistant Staphylococcus aureus (MRSA) antimicrobial stewardship in the 2021 Surviving Sepsis Campaign Guidelines, we sought to measure the use of vancomycin in the emergency department (ED) in the years preceding these recommendations.

Methods: A retrospective cohort study was conducted of all patients aged ≥ 18 years presenting to 5 emergency departments within a university-based health system who were given intravenous (IV) vancomycin during their ED index visit. The primary outcome assessed the proportion of patients with MRSA-positive blood cultures who received IV vancomycin in the ED. We also measured associations between clinical attributes associated with any MRSA infection.

Results: Of the 20,212 unique ED visits for patients who received IV vancomycin, 63% (n = 12,755) had at least 1 MRSA risk factor. Only 2.4% (n = 494) and 14.1% (n = 2850) of patients receiving IV vancomycin in the ED were found to have MRSA bacteremia or any MRSA-positive culture, respectively. A total of 3160 patients met Sepsis-3 criteria and received IV vancomycin, though 65% (n = 2064) had no MRSA risk factors. For any patient with culture-proven MRSA, 63.8% (n = 315) and 43.4% (n = 1236) received an MRSA antimicrobial in the ED. MRSA risk factors were not associated with MRSA bacteremia (≥1 MRSA risk factor: odds ratio, 1.3, 95% CI, 0.9-1.8) or an MRSA-positive culture of any type (odds ratio, 0.9, 95% CI, 0.7-1.1).

Conclusion: Within our hospital system, MRSA was an infrequent cause of bacteremia for patients presenting to the ED with sepsis or septic shock. Although vancomycin is frequently used in the ED, many patients with culture-proven MRSA did not receive MRSA antimicrobials. Notably, one-third of patients with culture-proven MRSA had no MRSA risk factors. MRSA risk factors were not predictive of culture-proven MRSA, thus highlighting the complexity of antimicrobial stewardship in the ED without validated clinical decision rules.